Exprolog

Exprolog is a logic programming language(DSL) like Prolog built on top of Elixir.

Build

Exprlog is no dependency.

% mix 

Using on iex

You must 'use Exprlog' on iex.

Example:

$ iex -S mix
Eshell V8.0  (abort with ^G)
Interactive Elixir (1.4.0-dev) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> use Exprolog
Cps
iex(2)> defrule append([], c, c) ## define append/3 base rule
true
iex(3)> defrule append([a|as], b, [a|cs]) do  ## define append/3 recursive rule
...(3)> append(as, b, cs)
...(3)> end
end
true
iex(4)> Exprolog.interprete(append([1,2,3], [4,5], a)) ## eval append/3
[status: true, query: {:append, [], [[1, 2, 3], [4, 5], {:_var, "a"}]},
 answer: [{"a", [1, 2, 3, 4, 5]}],    ## answer a is [1,2,3,4,5]
 goal: {:append, [], [[1, 2, 3], [4, 5], [1, 2, 3, 4, 5]]}]
iex(5)> fail()
fail()
nil
iex(6)> Exprolog.interprete(append(a, b, [1,2,3])) ## combination a,b ?
[status: true, query: {:append, [], [{:_var, "a"}, {:_var, "b"}, [1, 2, 3]]},
 answer: [{"a", []}, {"b", [1, 2, 3]}], # a: [], b: [1,2,3]
 goal: {:append, [], [[], [1, 2, 3], [1, 2, 3]]}]
iex(7)> fail() ## more ?
fail()
[status: true, query: {:append, [], [{:_var, "a"}, {:_var, "b"}, [1, 2, 3]]},
 answer: [{"a", [1]}, {"b", [2, 3]}], # a: [1], b: [2,3]
 goal: {:append, [], [[1], [2, 3], [1, 2, 3]]}]
iex(8)> fail()  ## more ?
fail()
[status: true, query: {:append, [], [{:_var, "a"}, {:_var, "b"}, [1, 2, 3]]},
 answer: [{"a", [1, 2]}, {"b", [3]}], # a: [1,2], b: [3]
 goal: {:append, [], [[1, 2], [3], [1, 2, 3]]}]
iex(9)> fail() ## more ?
fail()
[status: true, query: {:append, [], [{:_var, "a"}, {:_var, "b"}, [1, 2, 3]]},
 answer: [{"a", [1, 2, 3]}, {"b", []}], # a: [1,2,3], b: []
 goal: {:append, [], [[1, 2, 3], [], [1, 2, 3]]}]
iex(10)> fail() ## more ?
nil
iex(11)> Exprolog.interprete(append(a, b, c), [{"a", [1,2]}, {"b", [3]}])
[status: true, query: {:append, [], [[1, 2], [3], {:_var, "c"}]},
 answer: [{"c", [1, 2, 3]}], goal: {:append, [], [[1, 2], [3], [1, 2, 3]]}]
iex(12)> 

Introduction

What is Exprolog?

Prolog is a logic programming language based on first-order predicate logic. Exprolog is a domain specific language for logic programming built top of Elixir.

Logic programming language?

first-order predicate logic is completeness, and noncontradiction.

References

Syntax

RULE:: FACT | RULE

FACT::  'deffact' PREDICATE '(' ARGS ')'

RULE::  'defrule' PREDICATE '(' ARGS ')' |
        'defrule' PREDICATE '(' ARGS ')' 'do'
          EXPS
        'end'

EXP:: PREDICATE(ARGS) 
      | 'cut' '(' ')' 
      | 'fail' '(' ')' 
      | TERM '=' Arbitary-Elixir-Expression 

EXPS:: ':elixir' | EXPRESSIONS 

EXPRESSIONS:: EXP 
      | EXP NL EXPRESSIONS

PREDICATE:: Atom

ARGS:: 
   | TERM 
   | ARG, ARGS

TERM:: Atom | Number |List | Tuple | Var | EXP
NL:: '\n'

Builtin

atom/1 
integer/1
float/1
atomic/1
compound/1
var/1
true/0

Pure Prolog

0
s(0)
plus/3
natural_number/1
times/3

Core Library

append/3
member/2
sort/2
select/3
permutation/2
partition/4
append_dl/3